Part of the operation of a nuclear power plant is the removal and disposal of irradiated nuclear fuel assemblies. Most early reactors were originally built to store from three to five years' capacity of irradiated fuel assemblies in a storage pool. From the storage pool, the irradiated fuel assemblies could be reprocessed or sent to long-term storage. However, as a result of uncertainties in the federal policies relating to reprocessing of irradiated fuel and also in the establishment of permanent irradiated fuel dumps, on-site irradiated fuel storage facilities have been stressed to their capacity for storing these irradiated fuel assemblies. To prevent the forced shutdown of nuclear power plants as a result of the overcrowding of storage pools, a number of near-term irradiated fuel storage concepts have been developed and/or utilized.
One such near-term concept in use is the dry storage of irradiated fuel. Nonetheless, early developments in irradiated fuel dry storage in the United States anticipated that this would be a short-term measure, with removal of irradiated fuel to more permanent geologic storage required by Federal Law starting in 1998. As it became apparent that this would not happen, and that interim dry storage would be a larger scale and longer term effort, the following change occurred in the demands placed on dry storage systems.
As the initial inventory of low burnup, long cooled irradiated fuel residing in pools was transferred to dry storage, and as power plants increased the enrichment and burnup of their fuel, the need to store fuel with ever greater residual decay heat has grown. The fuel gives off heat from the decay of the radioactive elements, and so the storage system must be able to keep the fuel cladding cool enough that it does not deteriorate during the dry storage period without the use of active coolers such as fans. Early systems were developed with a capability for about 24 kW of decay heat per system; current needs are in excess of 40 kW.
Various structures have been developed to transport and store the irradiated fuel in secure canisters. One type of canister uses a lattice structure to form compartments to locate the fuel within the transport and storage canisters. The lattice structure is of “egg crate” design composed of interlocking transverse plates. However, existing baskets of egg crate design have used very expensive materials. Such materials include, for example, borated stainless steel, extruded profiles of enriched boron aluminum and metal matrix composites. Thus, a need exists of constructing transport and storage canisters from lower cost and more common materials.
A system was developed for horizontal modular dry irradiated fuel storage, as described in U.S. Pat. No. 4,780,269, the disclosure of which is hereby expressly incorporated by reference. However, there exists a need for improvements to that system. Embodiments of the present disclosure described herein are directed to fulfilling this and other needs.